propeller feathering while ground run

[cessnadriver]

TO: mshac and TomM.
Thanks guys for your replies/suggestions.
I replaced the oil relief valve plunger with one that was in better condition. Added three washers, but didn't seem to make a difference.
Oil pressure at start up is 40 PSI, and goes to 32-35 PSI after warm-up(10 minutes). At that time the prop slowly goes to feather. Yes I can lock the prop with a paddle back to low pitch. I can hear the latches lock on. Checked the cylinder pressures, cold, all but number 3 and 4 are 78/80 the others 60-62? Did the fuel in oil and check the pressure at the prop governor pad, suppose to be 20-50 PSI, mine is at 20 PSI. The engine only ran for 0.5 hour after overhaul so I'd say NO to break-in.
Thanks again for your questions and suggestions.
Regards, BILLS